Dental scan MDCT: comparison of dose levels and image quality

assessment between three centres in two European

countries S. Puggina, S. Galo, M. Calderone, L. Best, K. Katsari, R. Illing

Aims and objectives

To analyse the relationship between radiation exposure and diagnostic image quality of dental multidetector Computed Tomography (MDCT) protocols, to determine best practice and compare to published dose data from cone beam CT (CBCT). To determine the protocol with the lowest achievable CT dose for clinically appropriate image quality.

Why Dental MDCT?

- Common Examination!! - Standard Protocol

(mandible and/or maxilla) - Interesting dose comparison

with increasingly widespread CBCT

Methods and materials Study design and patient selection

Data from 90 patients who underwent dental MDCT examination were collected from three European centers. The patients were categorized by center into three groups of 30, with the first and second groups from Italy and the third group from Portugal.

Inclusion and exclusion criteria

Only mandible Dental MDCT. Clinical indication: tumors, cysts, inflamatory disease (endodontal and peryodontal), oroantral fistulas, dental implantology. No TMJ evaluation. Scanning Procedure and Protocols

Protocols from three MDCT scanner models were compared: 1. Discovery 750 HD 128 with ASiR (GEHC, Mil. USA) 2. LightSpeed VCT 64 with ASiR (GEHC, Mil. USA) 3. Somatom Sensation 64 with Care Dose option (Siemens Healthineers, Germany).

Methods and materials Data collection and analysis

The departments use GE HealthCare DoseWatchTM software to assist them in patient dose tracking and dose management. The protocol parameters and Total DLP values of each examination were exported from DoseWatch™.

Methods and materials Data collection and analysis

All images (volume and MPR) were anonymized and uploaded on a viewing platform prepared by Biotronics 3Dnet

Three experienced radiologists independently reviewed the whole examinations for Image Quality Assessment.

Image Quality Assessment was performed in terms of anatomy visualization and critical anatomical features using a 5 level scale for subjective quality, based on the clinical indications modified European Guidelines on Quality criteria for computed tomography . For the assessment of pathology visualization, a 3 level scale was used and scored.

A set of images was set as reference images, selected from the local database that complied to best practice guidelines

ANATOMY VISUALIZATION

CRITICAL ANATOMICAL FEATURES

PATHOLOGY VISUALIZATION

Definition of evaluation scales

Clearly lower than the reference images -2

Slightly lower than the reference images -1

Equal to the reference images 0

Slightly better than the reference images 1

Clearly better than the reference images 2

Definition of evaluation scales

Confident that the criterion is not fulfilled -2

Somewhat confident that the criterion is not fulfilled

-1

Indecisive whether the criterion is fulfilled or not 0

Somewhat confident that the criterion is fulfilled 1

Confident that the criterion is fulfilled 2

Definition of evaluation scales

Not present 1

Present 2

Undecisive 3

Visualization of: • mandible • mandibular canal • mental foramen • mandibular foramen • teeth roots

Visually sharp reproduction of: • mandible (cortical and trabecular bone) • mandible (width and height) • mandibular canal • teeth roots and mandibular canal relationship • relationship between lesions (lytic or sclerotic)

and the cortical margins and roots of the teeth

Presence of: • endodontal lesions • peryodontal lesions • bone lesion

ANATOMY VISUALIZATION

CRITICAL ANATOMICAL FEATURES

PATHOLOGY VISUALIZATION

Definition of evaluation scales

Clearly lower than the reference images -2

Slightly lower than the reference images -1

Equal to the reference images 0

Slightly better than the reference images 1

Clearly better than the reference images 2

Definition of evaluation scales

Confident that the criterion is not fulfilled -2

Somewhat confident that the criterion is not fulfilled

-1

Indecisive whether the criterion is fulfilled or not 0

Somewhat confident that the criterion is fulfilled 1

Confident that the criterion is fulfilled 2

Definition of evaluation scales

Not present 1

Present 2

Undecisive 3

Visualization of: • mandible • mandibular canal • mental foramen • mandibular foramen • teeth roots

Visually sharp reproduction of: • mandible (cortical and trabecular bone) • mandible (width and height) • mandibular canal • teeth roots and mandibular canal relationship • relationship between lesions (lytic or sclerotic)

and the cortical margins and roots of the teeth

Presence of: • endodontal lesions • peryodontal lesions • bone lesion

A one way Anova was performed to compare the median value of DLP and effective dose of the three Protocols

Statistic analysis and Results

Total DLP (mGy.cm)

Effective Dose (mSv)

MEAN 285,64 0,60

PROTOCOL 1 MEDIAN 287,37 0,60

MIN 236,87 0,50

MAX 344,90 0,72

Total DLP (mGy.cm)

Effective Dose (mSv)

MEAN 131,17 0,28

PROTOCOL 2 MEDIAN 124,71 0,26

MIN 82,71 0,17 MAX 201,63 0,42

DLP (mGy.cm) Effective

Dose (mSv)

MEAN 149,21 0,31

PROTOCOL 3 MEDIAN 141,18 0,30

MIN 113,69 0,24 MAX 305,61 0,64

• DLP varies significantly by protocol • Effective dose varies significantly by

protocol • Protocol 1 has significantly higher DLP

and effective dose than Protocol 2 and Protocol 3

• Non-significant statistical differences in DLP and effective dose variation in Protocol 2 and Protocol 3

Dosimetric parameters evaluation

Inter-rater reliability evaluation The data from Fleiss Kappa Comparison suggests good inter-rater reliability across critical anatomical features visualization and pathology evaluation . In regards to anatomy visualization Protocol 2 has significantly lower agreement than Protocol 1; no significant difference between the other protocols . According to the two tailed significant test of Pearson coefficient results, there is no significant correlation between DLP and fleiss' kappa for visualization of anatomy (proxy for image quality).

Statistic analysis and Results

Correlation between dose levels and image quality

DLP does not have a significant effect on visualisation scores.

Statistic analysis and Results Image quality evaluation

Two tailed t tests revealed significant differences in the visualization score between the protocols: • Protocol 1 has a significantly lower score than Protocol 2 • Protocol 3 has significantly higher scores than Protocol 2; both offer diagnostically

accurate images in visualization of expected and critical anatomical structures.

In particular, using a two tailed t test with unequal variances with Bonferroni correction: Anatomy visualization comparison:

• Protocols 2 and 3 have significantly higher scores than protocol 1 • Protocol 3 has significantly higher scores than protocol 2

Critical anatomical features comparison: • Protocols 2 and 3 have significantly higher scores than protocol 1 • Protocol 3 does not have significantly higher scores than protocol 2

Conclusions

The Protocol with the highest radiation dose, in this study, didn’t result in the production of high quality images.

The most appropriate scanning protocol selected, to standardize across the centers in this study, was the one that provided the lowest achievable radiation dose with diagnostically accurate image quality

Dose Monitoring and comparison of different CT scanners permit real optimization of protocols in terms both of image quality and radiation exposure, as well as comparison between vendors and models.

Protocol 2 (Mean Effective Dose 0,28 mSv) compared with CBCT published dose data, has significantly higher level of radiation dose.

Thanks for the Attention